Inconsistant operating temperature

[eqquus1]

We own a 1998 37' Aft Cabin powered by 3116 cats non electronic. The issue is temperature fluctuation on the starboard engine when running at 2600 rpm. The stbd engine temp increases to 195. The port stays rock solid at 180. I changed the thermostat last year. The impeller for the raw water has been changed. The heat exchanger had the raw water side opened and I chased every tube with a brass rod that fits the diameter and length perfectly. The output of water through the side of the boat looks good. The engine has about 1000 hrs on it. Any thoughts?

 

[Espos4]

Is it possible that you put in a 195 degree thermostat? the temperature should be stamped somewhere on the thermostat.

Does the temp ever go above 195?

 

[eqquus1]

It is definitely a 180 degree thermostat. And yes it has gone way over 195 unfortunately.

 

[doozie]

it could be the pump itself, had a similar issue new pump solved it.

 

[eqquus1]

A very qualified diesel mechanic who does some work for me has suggested that the oil cooler on 3116 cats tends to accumulate zinc materials over time and should be checked. That is the next thing that I am going to do. Does anybody have any thoughts?
i have not examined the engine yet but I presume that the oil cooler comes after the engine coolant heat exchanger....

 

[fwebster]

All of the cooling water for the 3116 passes thru the transmission oil cooler. The tubes are very small and easily visible if you remove the hose from the inlet side of the oil cooler. Your post said your temperature fluctuates, yet your description says at 2600 rpm the temperature rises to 190˚ and above, not fluctuates. If the temperature fluctuates, look for a big hunk of trash like an impeller blade or a broken off zinc or 2; if the temperature just rises as rpms rise, then then your cooling water flow is inadequate so look for fouled or stopped up tubes in the oil cooler.

And, for the record, these engines have a rated cruise rpm of 2400 rpm, not 2600.

 

[eqquus1]

Thank you for the information everyone. Frank sorry about the confusion, we cruise at 2400 rpm and there is NO fluctuation at this point. However, if we increase speed, the temperature rises to 190 and above. If we don't decrease speed it would be a problem. We will be looking into the oil cooler and let you know. Thanks again.